1. Field of the Invention
The present invention relates to a transmission system for a vehicle, particularly to a transmission system for a vehicle that performs a shift between gear positions and engagement/disengagement of a clutch in an interlocked manner by using a single actuator.
2. Description of Related Art
A transmission system for a vehicle in which a shift operation of a sequential-type staged transmission formed to be integral with an engine of a motorcycle or the like is performed using an actuator, such as an electric motor, is known in the art.
For example, Japanese Patent Laid-Open No. Hei 11-082734 discloses a transmission system for a vehicle in which a shift drum for switching between transmission gear trains and a shift clutch for momentary interruption of transmission of a rotational driving force are connected to a single shift spindle, and the shift spindle is rotated by an actuator so as to perform a shift operation while operating the shift drum and the shift clutch in an interlocked manner.
The shift spindle is configured to reciprocally turn between an initial position and a position of a predetermined angle (for example, 30 degrees) on a normal rotation side or a reverse rotation side in order to activate an intermittent feeding mechanism of the shift drum. On the other hand, the shift clutch is in an engaged state when the shift spindle is in the initial position, and the shift clutch is changed over into a disengaged state in the course of the shift spindle being brought to the predetermined-angle position.
In addition, in the transmission system for a vehicle described in Japanese Patent Laid-Open No. Hei 11-082734, for realizing both a shortening of the shifting time and a reduction in a shift shock, a special setting is adopted. Namely, in the former or first half of the shift operation, the shift spindle is driven at a high speed so as to swiftly change the shift position (gear position). On the other hand, in the latter or second half of the shift operation to the returning of the shift spindle into its initial position, the driving speed for the shift spindle is lowered so that the shift clutch is re-engaged gently.
In the technology described in Japanese Patent Laid-Open No. Hei 11-082734, however, the mode of operation of the actuator during the period from the time a shift command is inputted through a shift switch or the like to the time the re-engagement of the shift clutch is completed is previously determined. In this case, it is not taken into consideration to perform an optimum re-engaging operation for the shift clutch according to the running conditions of the vehicle, such as vehicle speed and throttle angle.